jack-a-lantern jac·ka·lan·tern uncommon noun 1. a large poisonous agaric with orange caps and narrow clustered stalks; the gills are luminescent Synonymsjack-o-lantern fungusjack-o-lanternOmphalotus illudens Related words Broader terms agaric Parts Omphalotus WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
